Local structure and dynamics in methylammonium, formamidinium and cesium tin(II) mixed−halide perovskites from 119Sn solid−state NMR,Journal of the American Chemical Society

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Local structure and dynamics in methylammonium, formamidinium and cesium tin(II) mixed−halide perovskites from 119Sn solid−state NMR
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2020-04-03 , DOI: 10.1021/jacs.0c00647
Dominik J Kubicki _{1,

2} , Daniel Prochowicz ₃ , Elodie Salager _{4,

5} , Aydar Rakhmatullin ₄ , Clare P Grey ₂ , Lyndon Emsley ₆ , Samuel D Stranks _{1,

7}

Affiliation

Organic–inorganic tin(II) halide perovskites have emerged as promising alternatives to lead halide perovskites in optoelectronic applications. While they suffer from considerably poorer performance and stability in comparison to their lead analogues, their performance improvements have so far largely been driven by trial and error efforts due to a critical lack of methods to probe their atomic-level microstructure. Here, we identify the challenges and devise a 119Sn solid-state NMR protocol for the determination of the local structure of mixed-cation and mixed-halide tin(II) halide perovskites as well as their degradation products and related phases. We establish that the longitudinal relaxation of 119Sn can span 6 orders of magnitude in this class of compounds, which makes judicious choice of experimental NMR parameters essential for the reliable detection of various phases. We show that Cl/Br and I/Br mixed-halide perovskites form solid alloys in any ratio, while only limited mixing is possible for I/Cl compositions. We elucidate the degradation pathways of Cs-, MA-, and FA-based tin(II) halides and show that degradation leads to highly disordered, qualitatively similar products, regardless of the A-site cation and halide. We detect the presence of metallic tin among the degradation products, which we suggest could contribute to the previously reported high conductivities in tin(II) halide perovskites. 119Sn NMR chemical shifts are a sensitive probe of the halide coordination environment as well as of the A-site cation composition. Finally, we use variable-temperature multifield relaxation measurements to quantify ion dynamics in MASnBr3 and establish activation energies for motion and show that this motion leads to spontaneous halide homogenization at room temperature whenever two different pure-halide perovskites are put in physical contact.

中文翻译：

来自 119Sn 固态 NMR 的甲基铵、甲脒和铯锡 (II) 混合卤化物钙钛矿的局部结构和动力学

有机-无机锡（II）卤化物钙钛矿已成为光电应用中卤化铅钙钛矿的有前途的替代品。虽然与铅类似物相比，它们的性能和稳定性要差得多，但迄今为止，由于严重缺乏探测其原子级微观结构的方法，它们的性能改进主要是通过反复试验来推动的。在这里，我们确定了挑战并设计了 119Sn 固态 NMR 协议，用于确定混合阳离子和混合卤化物锡 (II) 卤化物钙钛矿的局部结构及其降解产物和相关相。我们确定 119Sn 的纵向弛豫在此类化合物中可以跨越 6 个数量级，这使得明智地选择实验 NMR 参数对于可靠检测各种相至关重要。我们表明，Cl/Br 和 I/Br 混合卤化物钙钛矿以任何比例形成固体合金，而 I/Cl 组合物只能进行有限的混合。我们阐明了基于 Cs、MA 和 FA 的锡 (II) 卤化物的降解途径，并表明无论 A 位阳离子和卤化物如何，降解都会导致高度无序、性质相似的产品。我们检测到降解产物中存在金属锡，我们认为这可能有助于先前报道的锡 (II) 卤化物钙钛矿的高导电性。119Sn NMR 化学位移是卤化物配位环境以及A 位阳离子组成的敏感探针。最后，

更新日期：2020-04-03

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